The present disclosure relates to a wind energy system and a method for operating a wind energy system. In particular, the present invention relates to a tilt adjustment system for a wind energy system.
Rotation axes of hubs of wind energy systems are often provided with a tilt angle with respect to a perpendicular to an axis through the tower to create a required static clearance between tips of the rotor blades mounted to the hub and the tower of the wind energy system. The static clearance depends inter alia on maximum expected wind conditions and on the material properties of the rotor blades. The clearance is required to avoid contact between rotor blades and the tower. However, this positive tilt angle of the rotation axis of the hub of the wind turbine results in a misalignment angle between the axis of rotation of the hub and the rotor blades and the direction of the wind. Accordingly, the wind encounters the rotor blades under a misalignment angle.
Additionally, the inflow direction of the wind to the rotor is generally misaligned with the horizontal, a natural phenomenon known as upflow. In contrast to the tilt angle, the upflow angle, or the angle between the upflow and the horizontal, is generally variable, depending on wind and site conditions. Hence, a misalignment angle is the sum of the tilt angle and the upflow angle.
The misalignment angle results in a reduction of the area covered by the rotor blades perpendicular to the wind direction. Therefore, energy yields can be reduced compared to the situation of perfectly perpendicular inflow to the rotor plane. Furthermore, inflow misalignment can contribute to unsteady loading, which makes operation of the wind energy system more complicated. Thus, a wind energy system is desired which reduces the misalignment angle, especially in wind conditions where the maximum power of the turbine has not been reached.